martes, 7 de octubre de 2014

In total
1,149 cases were laboratory-confirmed between August and December 2012

On 15
August 2012, an increase in the number of Salmonella
Thompson cases was noticed by the Salmonella surveillance in the
Netherlands. A case–control study was performed, followed by a food
investigation.

In total 1,149 cases were laboratory-confirmed
between August and December 2012 of which four elderly (76–91 years) were
reported to have died due to the infection. The cause of the outbreak was
smoked salmon processed at a single site.

The smoked
salmon had been continuously contaminated in the processing lines through
reusable dishes, which turned out to be porous and had become loaded with
bacteria. This is the largest outbreak of salmonellosis ever recorded in the
Netherlands.

The
temporary closure of the processing site and recall of the smoked salmon
stopped the outbreak. An estimated four to six million Dutch residents were
possibly exposed to the contaminated smoked salmon and an estimated 23,000
persons would have had acute gastroenteritis with Salmonella Thompson during this outbreak.

This
outbreak showed that close collaboration between diagnostic laboratories,
regional public health services, the national institute for public health and
the food safety authorities Although a case–control study was started
immediately after detection of the outbreak, it took several weeks before the
cause could be identified.

The main
reason for the delay was the low number of cases in the beginning of the
outbreak and the low number of completed questionnaires, from cases and
controls, available for analysis.

A number of
other possible sources were suggested before the analysis led to salmon. This
was most likely caused by the relatively low number of cases reporting
consumption of smoked fish (62/108, 57%). This can be due to recall bias, but
also because the salmon was incorporated in other products, for example
pre-sale ready-to-eat salads or as part of a menu in the catering industry.